1. Field of the Invention
This invention generally relates to devices for and methods of contacting solids with fluids and specifically to nozzle devices, i.e. apparatus means including a nozzle or jet which is operated with a fluid that may but need not be gaseous.
2. Prior Art
Nozzle devices are widely used in yarn processing and this is a preferred yet not the only field of interest for the present invention. For example, yarns that comprise or consist of man-made fibres including all-synthetic fibres frequently require some treatment involving texturizing and/or intermingling of the filaments, or filament groups, which together form the multifilament product yarn, and a common element of such treatment is contacting the yarn with a fluid, such as air or steam, generally under high-temperature and high-pressure or high-turbulence conditions of the fluid.
Typically, conventional nozzle devices constitute the inlet portion of a texturizing system, also termed jet system, normally operating with hot air or steam; the purpose of such systems is to first plasticise the yarn and then to submit it to the impact of pressure and/or turbulence so as to deform the yarn for imparting crimp and to obtain a more bulky yarn product. Essentially, a texturizing system thus consists of a first portion, also termed induction side of the system, for taking the yarn into and through a channel, and of a second portion, e.g. a chamber which provides for a larger area into which the yarn is forwarded at high velocities and where the yarn is forced against blades or chamber segments so as become crimped or otherwise modified under heat and pressure.
However, commercially available texturizing jet systems tend to exhibit problems at the induction side, notably when processing yarns that consist of differing filaments, such as multicolored yarns consisting of filament portions that are differently coloured, e.g. melt-spun in groups from polymers admixed with various colours or dyes, or consist of differing polymer species. Very small irregularities caused in the manufacture or by wear of the jets may cause rather substantial flow differences tending to cause irregular induction and convection of the processed yarns. For example, when processing yarns composed of differently coloured filament groups, irregular induction tends to change the positional filament order, i.e. the relative positions of the yarn constituent fibres, and only in a yarn consisting of identical filaments would such changes be without detrimental consequences. As soon as differing filaments or filament groups are used, a change of the positional order of the filaments in the yarn tends to change the visible or tangible yarn properties, e.g. colour appearance, and cause subsequent problems of quality, uniformity, and colour variation.
Since it is the exception rather than the rule that different jets (e.g. at different parts of the same production plant) behave identically with regard to induction, it will be understood that nozzle structure and nozzle operation can pose extremely important problems in many fields of yarn production if consistent and reproducible quality parameters are to be achieved.